Magnetoresistive sensors can include anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), tunnel magnetoresistive (TMR) and other technologies, referred to collectively as xMR technologies. XMR sensors can be used for a variety of applications, including magnetic field and current sensors, speed sensors, rotation sensors and angle sensors, among others.
The accuracy of AMR angle sensors is limited by magnetic anisotropy and hysteresis effects. Key influencing factors are magnetic domains near the structure edge because the shape anisotropy caused by the demagnetizing field is strongest near the edge. Furthermore, defects at the edge related to the etch process can act as pinning centers that potentially lead to domain generation responsible for hysteresis effects. While shape anisotropy can be reduced by using wider AMR stripes, this requires bigger chip size as well as a larger signal field magnet.
In GMR and TMR angle sensors, however, AMR effects are parasitic and undesirable. TMR structures typically require a top contact and a bottom contact to induce a current perpendicular to the sensor plane. If a TMR current-in-plane (CIP-TMR) concept is used, the same structures as for GMR sensors can be used, obtaining a higher sensor signal. The main reasons for angle error remaining after full compensation are magnetic anisotropy effects and, as previously mentioned, AMR effects, which are considered parasitic. AMR effects can be suppressed by using shaped meanders having orthogonal strip length axes. In order to reduce any remaining anisotropy effect, the strip width can be made wider, thereby increasing the chip size, which is undesirable and increases cost.
Therefore, a need remains for an improved xMR sensor.